# Statistics

posted by .

The average age of chemical engineers is 37 years with a standard deviation of 4 years. If an engineering firm employs 25 chemical engineers, find the probability that the average age of the group is greater than 38.2 years old. If this is the case, would it be safe to assume that the chemical engineers in this group are generally much older than average.

Assume that the mean systolic blood pressure of normal adults is 120 millimeters of mercury and the standard deviation is 5.6. Assume the variable is normally distributed:

A)If an individual is selected, find the probability that the individual;s pressure will be between 120 and 121.8

B) If a sample of 30 adults is randomly selected, find the probability that the sample mean will be between 120 and 121.8

At a large publishing company, the mean age of proofreaders is 36.2 years, and the standard deviation is 3.7 years. Assume the variable is normally distributed:

A) If a proofreader from the company is randomly selected, find the probability that his or her age will be between 36 and 37.5 years.

B) If a random sample of 15 proofreaders is selected, find the probability that the mean age of the proofreaders will be between 36 and 37.5 years

• Statistics -

Z = (Sample mean-population mean)/SEm = (38.2-37)/SEm

SEm (Standard Error of the Mean) = SD/√(n-1)

Find table in the back of your statistics text labeled something like "areas under normal distribution" to find the proportion related to that Z score.

Use similar process for B sections of other questions

A) Z = (score-mean)/SD = (121.8-120)/5.6

Use the same table and similar process for both A questions.

The difference between A and B is that the former deals with a distribution of scores and the latter deals with a distribution of means.

## Similar Questions

1. ### statistics

According to Beautiful Bride magazine, the average age of a groom is now 26.2 years. A sample of 16 prospective grooms in Chicago revealed that their average age was 26.6 years with a standard deviation of 5.3 years. What is the test …
2. ### statistics

An April 15, 2002 report in Time Magazine stated that the average age for women to marry in the United States is now 24.9 years of age. If the standard deviation is assumed to be 4.9 years, find the probability that a random sample …
3. ### statistics

An April 15, 2002 report in Time Magazine stated that the average age for women to marry in the United States is now 24.9 years of age. If the standard deviation is assumed to be 4.9 years, find the probability that a random sample …
4. ### STATISTICS

An April 15, 2002 report in Time Magazine stated that the average age for women to marry in the United States is now 24.9 years of age. If the standard deviation is assumed to be 4.9 years, find the probability that a random sample …
5. ### statistics

An April 15, 2002 report in Time Magazine stated that the average age for women to marry in the United States is now 25.1 years of age. If the standard deviation is assumed to be 4.6 years, find the probability that a random sample …
6. ### Statistics

An April 15, 2002 report in Time Magazine stated that the average age for women to marry in the United States is now 24.5 years of age. If the standard deviation is assumed to be 4.1 years, find the probability that a random sample …
7. ### Quantitative Analysis for Business

The ages of a group of 50 women are approximately normally distributed with a mean of 48 years and a standard deviation of 5 years. One women is randomly selected from the group, and her age is observed. A) Find the probability that …
8. ### statistics

An April 15, 2002 report in Time Magazine stated that the average age for women to marry in the United States is now 25.6 years of age. If the standard deviation is assumed to be 4.1 years, find the probability that a random sample …
9. ### Statistics

An April 15, 2002 report in Time Magazine stated that the average age for women to marry in the United States is now 25.9 years of age. If the standard deviation is assumed to be 4.3 years, find the probability that a random sample …
10. ### statistics

The average age of doctors in certain hospital is 43 years old. Suppose distribution of ages is normal and the standard deviation is 8.0 years. If 25 doctors is chosen at random for a committee, find the probability the average age …

More Similar Questions